Vacuum pumping apparatus



April 1, 1952 J. H. BLACK ET AL VACUUM PUMPING APPARATUS Filed Sept. 1,1950 BY 91h JUDD H. BLACK HORACE G. WARREN INVENTORS ATTORNE rs PatentedApr. 1, 1952 VACUUM PUMPING APPARATUS Judd H. Black and Horace G.Warren, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., acorporation of New Jersey Application September 1,1950, Serial No.182,862

This invention relates to apparatus for producin vacuum and isparticularly concerned with vacuum pumps of the type wherein organicpump fluid vapors are passed through paired ejector and difiuserelements and condensed.

It is an object of this invention to provide improved apparatus forproducing vacuum.

It is a further object of this invention to provide improved ejectorpumps of the type employing organic pump fluid vapors for evacuation inthe high vacuum range.

Another object of the invention is to provide a high vacuum pump of theejector type having a more compact structure than obtainable when spentpumpiiuid is returned to the pump boiler by gravity flow alone.

Another object of the invention is to provide a high vacuum pump of theejector type having no movable parts ordinarily subject to mechanicalfailure.

Another object of the invention is to provide acting means for returningcondensed organic pump fluid to the boiler against pressure in theboiler.

Another object of the invention is to provide a high vacuum pump of theejector type including means for returning condensed pump fluid from thepaired ejector-diiiuser elements to the boiler of the pump againstpressure in the boiler,

which means is responsive to changes in the pressure in said boiler.

Another object of the invention is to provide means for positivelyimpelling condensate from the ejector-diffuser assembly to the boiler ofa high vacuum pump without increasing the power consumption of the pumpto an objectionable degree.

Another object of the invention is to provide ahigh vacuum ejector pumpof the type employing organic pump fluid and including means for"utilizing a portion of the pump fluid vapors to return condensed pumpfluid from the pumping zone of the pump to the boiler against boiler 3Claims. (01. 230--101) a high vacuum ejector pump including positivelyferred form.

Vacuum pumping apparatus embodying this invention is of the type whereinvapors of organic pump fluid produced in a, suitable boilerare passedthrough paired ejector and difl'user elements, condensed and returned tothe boiler, the pump fluid vapors exerting a pumping action by passagethrough the paired ejector and difiuser elements whereby a systemconnected to the pumpin apparatus is evacuated.

In the preferred embodiment of the invention as illustrated in thedrawing, the vacuum pumping apparatus comprises pumping means adapted tobe connected to the system to be evacuated, vapor-generating meansconnected to the pumping means for delivering vaporized pump fluid tosaid pumping means, and condensate return means connecting said pumpingmeans with said vapor-generating means.

The pumping means of the preferred apparatus comprises a diiiuserelement It! and an ejector element H arranged in pumping relation withthe nozzle of ejectorelement H directed into the throat of diffuserelement ID. A condenser coil I 2 connected to a source'of COOIiIlg'fluid (not shown) is positioned around the diffuser element It] in heatconducting relation therewith, coil I2 extending around at least theportion of diffuser element In remote from ejector element H andpreferably around element I 0 substantiall throughout the length ofelement 10.

The vapor-generating means comprises a boiler l3 spaced below thepumping means and adapted to contain a body of organic pump fluid, suchas a phalate ester or sebacate ester or the like, and including asuitable heater element 14. such as an electrical immersion heater orother conventional heating means. Boiler I3 is connected to ejectorelement I l of the pumping means by primary vapor conduit l6, conduit l6being of the lower end of diffuser tube l'lwith boiler 13,

a jet nozzle 2| directed downwardly into the throat of diii'user tubeand a secondary vapor conduit 22 connecting jet nozzle 2| with primaryvapor conduit It at a point alon primary vapor conduit IB between boileris and ejector element H.

In the preferred embodiment, diffuser element H! in accordance withconventional construction practices is flared at the low pressure end ofthe element l adjacent ejector element H and is convergent fromthe lowpressure end toward a constricted throat and thence divergent at thehigh pressure or exhaust end of diffuser element Ill. Diffuser elementIt includes an inlet port 23 at the low pressure end of the diffuserelement It, which port 23 is adaptedto be connected to the system to beevacuated. An outlet or exhaust port 24 at the high pressure end ofdiffuser element It! isarranged for connection loat a point-behind themouth of ejector element H: whereby backstreaming of pump fluid vaporsinto thespacebeing evacuated is minimized.

Referring to the condensate return means,

diffuser tube I! comprises a downwardly convergent upper portion, aconstricted throat and a downwardly divergent lower portion. Jet nozzle2|, which is preferably flared outwardly to-the jet mouth, is directeddownwardly into I theconvergent upper portionof diffuser tube 9'!towards the constricted throat of difiuser tube 1?. Condensate. conduitI8 connecting diffuser ele- 'ment, 1 i! and diffuser tube ll opens intothe upper end-10f diffuser tube I! at a point not lower than themouthofjet nozzlell. embodiment wherein diffuser element It] isgenerally horizontally disposedandcooled by con- .denser coil I21substantially throughout its length, condensate. conduit I8 is branchedand connected In the preferred to both ends of diffuser element Ill.Secondary eondensateconduit [9 connecting the lower end of-diffuser-tubeH with boiler l3 desirably opens into boiler 43- below the normal levelof pump 7 fluid-in the boiler I3.

' The secondary vapor conduit 22 connecting jet nozzle 2|- with; theprimary vapor conduit i6 is desirably of substantially smaller diameterthan the primaryvapor conduit [6. In order to condraining pump fluidfrom the boiler. If desired,

. amanometer 21 can be connected to the boiler l3 ment It and expandinto the divergent high pres sure end of difluser element l0 therebyevacuating the system connected to inlet port 23.

During passage through diffuser element iii,

' condensate is impelled by the pump fluid vapors serve heat, boiler [3,primary vapor conduit i3 7 and secondary vapor conduit 22 are laggedthroughout their extent as indicated at 28, 28. Drain cap 25' on boiler13 provides means for and diffuser element it for measurin the boilerp-p essura circulated through the condenser coil. I2. A suitable o a iump fluid s c -a phalate te sebacate ester, tetrasilane or otherwell-.lrnown pump fluid is progressively vaporized in boiler 13 by meansof heater element M. Pump fluid vapors generated in the boiler arechanneled upwardly through primary vapor conduit Hi to ejector-elementII. The vapors are. ejected h .uehthe mouthoi e ec l m n p 1 are an thcons r cted j hroa or; d fl s r l which are conducted from the primaryvapor conduit it to jet nozzle 2! by secondary vapor conduit 22, suchvapors being passed with the condensate downwardly through diffuser tubeit. The vapors issuing into diifuser tube H; from jet nozzie 2i expandin volume and condense at least in part upon coming in contact with therelatively cooler condensate thereby serving to preheat the condensatebefore return to the boiler. As the condensate and vapors passdownwardly through the convergent upper portion of the diffuser tube ll,the diminishing volume'of the tube causes the fluid mixture to increasein velocity and decrease in pressure. After passing through theconstricted throat of diffuser tube ll, the fluid mixture decreases invelocity and increases in pressure upon passage downwardly through thedivergent lower portion of diffuser tube l? whereby condensate is forcedbackinto' boiler it through the second condensate conduit it against t.e pressure in the boiler. Since'the primary and secondary vapor conduitsare lag fifi and the heat of the vapors impelling condensate in thecondensate return means is used to preheat the condensate, there is verylittle loss in energy due to operation of the condensatereturn means.The pump does not depend upon a hydrostatic head of condensate forreturntotthe .boiler against boiler pressure and hence the pumpingapparatus, can be constructed- --velocity and hence provide greaterpressure. for

returning condensate to the boiler. whereby the condensate return meansis automatically responsive to pressure changes in the boiler. "Thevacuum pumping apparatus embodying the invention can thereby be operatedat'high boiler:

pressures resulting in an increased pumping rate and the ability tooperate against a higher-forepressure. j

While the invention has; been described inconsiderable detail withreference to a preferred embodiment thereof, it will be understoodthatvariations and modifications can be fifififite-d in t a a u od in h iventionw thi the spirit and scope of the invention'as illustrated in thedrawing and described he reinaboue and as defined in the appendedclaims.

What We claim is:

1 Vacuum pumping wherein organic pump fluid vapors are passed throughpaired ejector and diffuser elementsiand a rat s. of the-typ Vcondensed, said apparatus comprising in combination vacuum pumping meansincluding paired ejector and diifuser elements, a boiler positionedbelow and spaced from said vacuum pumping means, vapor-channeling meansconnecting said boiler and said ejector element, and means for returningcondensate from said pumping means to said boiler against pressure insaid boiler, said means for returning condensate comprising a downwardlydirected diffuser tube between said pumping means and said boiler, acondensate return conduit connecting said pumping means with an upperportion of said diffuser tube, a second conduit connecting a lowerportion of said diffuser tube with said boiler in a lower zone of saidboiler below the normal liquid level in said boiler, jet nozzle meansdirected downwardly into said diffuser tube, and a vapor conduitconnecting said jet nozzle means and said vapor-channeling means.

2. Vacuum pumping apparatus of the type wherein organic pump fluidvapors are passed through paired ejector and diffuser elements andcondensed, said apparatus comprising in combination vacuum pumping meansincluding an ejector element and a diffuser element arranged in pumpingrelation, said pumping means having an inlet port in a low pressure zoneof said pumping means and having an exhaust port in a higher pressurezone of said pumping means, condenser means arranged in heat-conductingrelation with said difiuser element and arranged for condensing organicpump fluid vapors passing through said diflfuser element, a boilerpositioned below and spaced from said pumping means, a primary vaporconduit connecting said boiler and said ejector element, and means forreturning condensed pump fluid from said pumping means to said boileragainst pressure in said boiler, said means for returning condensed pumpfluid comprising a downwardly directed diffuser tube disposed betweensaid pumping means and said boiler, said diffuser tube including adownwardly converging upper portion and a downwardly diverging lowerportion, a condensate return conduit connecting said pumping means withsaid upper portion of said diffuser tube, a second conduit connectingsaid lower portion of said diffuser tube with said boiler, jet nozzlemeans directed downwardly into said upper portion of said diffuser tube,said condensate return conduit being connected to said diffuser tube ata zone not lower than said jet nozzle means, and a secondary vaporconduit of substantially a lesser cross-section than said primary vaporconduit and connecting said jet nozzle means and said primary vaporconduit.

3. Vacuum pumping apparatus of the type wherein organic pump fluidvapors are passed through ejector and diffuser elements arranged inpumping relation and condensed, said apparatus comprising in combinationa generally horizontally disposed diffuser element having a convergentlow pressure portion and a divergent high pressure portion, an ejectorelement directed into said convergent low pressure portion, a boilerspaced from and below said diffuser element, a primary vaporconduitconnecting said boiler with said ejector element, an inlet port in thelow pressure portion of said diffuser element, an outlet port in thehigh, pressure portion of said diifuser element, a condenser coil. forcarrying cooling fluid disposed around said diffuser element inheat-conducting relation therewith, and means for returning condensedpump fluid from said diffuser element to said boiler against pressure insaid boiler, said means comprising a generally vertically disposeddiffuser tube positioned below said diffuser element and above saidboiler and having a downwardly convergent upper portion and a downwardlydivergent lower portion, a condensate conduit connecting said diffusertube with said upper portion of said diffuser tube, a second condensateconduit connesting said lower portion of said diffuser tube with saidboiler in a zone of said boiler below the normal liquid level in saidboiler, a flared nozzle directed downwardly into said convergent upperportion of said diffuser tube, and a secondary vapor conduit ofsubstantially lesser diameter than said primary vapor conduit connectingsaid flared nozzle with said primary vapor conduit, said first-namedcondensate conduit being connected to said diffuser tube at a zone notlower than said flared nozzle.

JUDD H. BLACK, HORACE G. WARREN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

